Encephalitozoon Cuniculi in Rabbits

Encephalitozoon cuniculi, otherwise known as E.cuniculi or E.C. for short, is a parasite that infects rabbits.

Encephalitozoon cuniculi, otherwise known as E.cuniculi or E.C. for short, is a parasite that infects rabbits. For a long time, it has been unclear what type of parasite E.C. actually is but we now think that it is a fungus.

Many rabbits are infected with E.C. but only a few will show signs of the infection and this is because it’s the animals reaction to the parasite that is the problem, rather than the presence of the parasite itself as such.
The most common organs affected by E.C. are the brain and the kidneys. Rabbits will form granulomas around the parasite, which replace the healthy, normal brain and kidney tissue. This leads to damage of the kidneys and brain tissue resulting in the typical clinical signs. E.C can also affect the eyes, if the foetus is infected whilst it’s in the uterus.
It is also important to remember than E. Cuniculi is a zoonotic disease, which means the parasite can affect humans. It is usually only immunocompromised people that can be affected by E.C. and cases are rare.

What are the clinical signs?
Clinical signs of E. Cuniculi include:
Head tilt
Paralysis / weakness effecting the hind legs
Wobbliness or ataxia
Rolling over continuously
Uveitis (if infected whilst in the uterus)
Urinary incontinence (urinating on themselves)
Drinking excessively
Urinating excessively
Reduced appetite

Clinical signs can vary greatly between individual rabbits. Some rabbits will only have mild clinical signs whereas other rabbits are severely affected and are unable to stop rolling over and cannot eat or drink on their own. Quality of life will need to be discussed if your rabbit is severely affected and you may need to consider if its kinder for your rabbit to be euthanised.

How is E.C. transmitted?
Spores are shed in the infected animal’s urine and can spread via food and water contaminated by the urine or by inhaling the spores. Transmission can also occur via the placenta from the mother rabbit to her unborn babies.

How is E.C. diagnosed?
Your vet may suspect E.C. on initial clinical exam, but there are other causes of head tilt and urinary tract disease and so it is important to perform further diagnostics tests if finances allow. The most common tests performed are:

Serology: this blood test looks at your rabbit’s antibody levels and can help your vet work out if your rabbit has been exposed to E.C. previously and whether they are currently affected by the parasite. Sometimes this test needs to be repeated after 4 weeks to see how the antibody levels change over time.

General blood test: It is particularly important to check your rabbit’s renal values to see how their kidneys are coping

Urine sample:this test can be useful at ruling out other causes of urinary tract signs such as bacterial infection and crystals

How is E.C treated?
E.C. is treated with Fenbendazole, which is a liquid worming formula that is usually given for 28 days. Your vet may also prescribe other medications to support your pet, especially if they are severely affected by the parasite and are struggling to eat and drink on their own.

What’s the prognosis?
Many rabbits that are affected with E.C. will go on to live long and happy lives but this does depend on how severely the rabbit is affected by the parasite. Some rabbits will have long term kidney issues due to the parasite and in some rabbits the neurological signs do not completely resolve.

If you are concerned that your rabbit may have E. cuniculi or if your rabbit has been diagnosed with E. cuniculi and you would like further support and advice, our Vet on the Net team of experienced vets are here to help!

Dr Louise Abuzet BVM&S CertAVP(ECC) CertAVP (ZooMed) BSc(HONS) MRCV
RCVS Advanced Practitioner in Emergency and Critical Care
2nd December 2020